HLTB15H3 Lecture Notes - Lecture 4: Absolute Difference, Attributable Risk, Cohort Study
Not randomly selected groups: limits: study exposures, can calculate incidence, temporal sequence, unbiased, natural history of disease, strengths: large size needed, cost, loss to follow up, changes to exposure, long time period, prospective (concurrent) Identify exposure in present and follow over time to determine future incidence of disease: retrospective (historical, use past records to determine exposure status at some time in past and determine current/ future incidence of disease. Identify study population and who is exposed/unexposed: select from a defined population (exposure status measured at start) and select based on exposure, follow groups over time, length depends on induction and latency periods; study design; age of persons. Induction: time btw cause of disease and disease onset: latency: time btw disease onset and symptoms, diagnosis, compare outcomes in both groups, relative risk (risk ration, rate ratio, odds ratio not ideal, attributable risk, survival/cumulative events. Probability of disease occurrence: compare incidence of outcome in exposed and unexposed.